Improvement in balanced slide-valves



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NJETERS. PHOTO-LFINDGRAPHER. WASHINGTON UNITED oSTATES PATENT @eineno JAMES RANKIN, 0F DETROIT, MICHIGAN.

IMPROVEMENT IN BALANCED SLIDE-VALVES.

Specification forming part of Letters Patent- NO. 4 7,453. (lated April 25, 1865.

To @ZZ whom it ntay concern:

Beit known that l, JAMES RANKIN, of Detroit, in the county of Wayne and State of Michigan, have invented a new and Improved Balanced Slide-Valve; and Ido hereby declare that the following is a i'ull, clear, and exact description thereof, which will enable those skilled in the art to make and use the same, reference being had t0 the accompanyingdrawings, forming part of this specification, in Which- Figure l represents a longitudinal vertical section of this invention, the line mx, Fig. 2, indicating the plane ot` section. Fig. 2 is ahorizontal section of the same, the plane ot'seetion being indicated by the line y y, Fig. l.

Similar letters of reference indicate corresponding parts.

The object of this invention is to balance the pressure of the steam on the back of a slidevalve in such a manner that the same works equally free under a pressure of one hundred pounds or more to the square inch as it does in the open atmosphere. This object is obtained by combining with the valve a piston through a series ot' intervening levers, rockers, and links in such a manner that the upward pressure ofthe steam on the piston counterbalanees the downward pressure on the back of thel valve, and the valve is perfectly balanced.

A represents the valve-chest, the bottom of' which formsthe seat for the slidevalve B, and a reciprocating motion is imparted to this vtlve by means ot' the rod C in the usual manner. From the back of the valve rise twolugs, a, which form the bearings for the fulcrnmpins b of the lever D, which is supported by said pins at about the middle of its length. One end of said lever is provided with a notch, c, which rests upon the upper end ot' a rocker, E, that is stepped in suitable bearings, d, on the. bottom ofthe valve'chest. rlhe opposite end of the lever D is suspended from a link, F, which connects by a pivot, e, with a lever, G, one end of which rests upon a knife'ed ge bearing, f., which is rigidly connected to the side of the valve-chest, whereas its other loose end extends through a slot in the piston-rod g. This rod extends from a piston, H, which is fitted into a cylinder, I, supported by the top of the steam -chest and open at its inner end. An aperture, h,inthetopofthe cylinder' forms an escape forthat portion oi'steam which may pass the piston. i

1f steam is admitted to the steamehest, it forces the piston up and the valve down, and the connection between the piston and valve and the areas of said parts are so proportioned that the upward pressure on the piston just balances the downward pressure on the valve. y

At the same time the valve is allowedto move freely on its seat, the lever I) being so arranged thatit partakes of the vibrating motion of the valve.

The pressure which holds the valve down on its seat can be easily regulated bychanging the position of the pin e, which connects the link F with the lever G. It this pivot is moved closer to the knife-edge bearing f, the power which tends to raise the valve from its seatis diminished, and by removing the pin c from the knife-edge bearingf closer to the pister.-

rod the upward pressure is diminished, and

consequently the mpressure which holds the valve down on its seat is increased.

By these means the slide-valve can be adjusted so nice'. y that it works equally free under a high pressure as it does'uhen the steam is shut oit', and that it is held down on its scat JAMES RANKKN. Witnesses J oHN FULLER, B. SPARLING. 

